Historically, various electronic assembly manufacturers have used a pressure sensitive adhesive (PSA) to bond an unpopulated substrate, e.g., printed circuit board (PCB), to a metal backplate. In general, the metal backplate has provided rigidity for the PCB and has protected the PCB from mechanically induced stresses. Usually, the PCB and backplate have been fed into a roller machine that includes one or more rollers that have applied pressure between the unpopulated PCB and backplate to activate a PSA (positioned between the PCB and backplate) and attach the PCB to the backplate. By applying pressure from one end of the assembly to the other end of the assembly, the roller machine has usually minimized air trapped between the PCB and the backplate. In such prior art assemblies, the backplate has been substantially flat such that no surface of the plate extended above a top surface of the PCB. This backplate surface limitation has been necessary due to the fact that the roller must contact the PCB to ensure activation of the PSA and, in turn, bonding of the PCB to the backplate. Unfortunately, the utilization of a flat backplate has generally negatively impacted the cost and design of the electronic assembly, as assemblies with flat backplates have required multiple additional mechanical panels to form a product enclosure.
Further, electronic assemblies that have first bonded an unpopulated PCB to a backplate have required that the PCB be populated after bonding of the PCB to the backplate. After population, the populated PCB and its associated backplate have both then been placed in a reflow oven, to initiate a solder reflow process at a desired temperature. Heating the mass of the backplate to the desired temperature has required additional energy which has increased the cost of the assembly. Further, the cooling time of the assembly has been increased as the backplate, due to its mass, cools more slowly than the PCB (and its associated electrical components) and, thus, has increased a processing time of the assembly. Additionally, when an electronic assembly manufactured in this manner fails an electrical test, the electrically defective assembly has generally been scrapped, as opposed to being reworked, due to the difficulty in reworking a populated PCB that is bonded to a backplate. Moreover, the reflow solder profile for such assemblies has been more complicated and, in turn, more expensive.
What is needed is a technique for bonding a populated (and electrically tested) substrate to a backplate. It would also be desirable if the technique allowed the backplate to be utilized as a more significant portion of a product enclosure.